669 research outputs found
Optimization of a Porous Electroosmotic Pump, used in Thermal Cooling System of Power Electronics
International audienceThe liquid cooling of electronic components is generally implemented by a mechanical pump, which requires a minimal maintenance to ensure the reliability of the device. To solve this problem, it is proposed to replace the mechanical pump by a static one, for example an electro-osmotic (EO) pump. In this paper, firstly we present the theory of the electro-osmosis phenomena, and a model of a porous EO pump. Then an optimization of a porous EO pump made of sintered silica is presented. It was found that for any porous EO pump the optimum operating point of the pump is determined by controlling the diameter of the effective pore radius of the porous silica and the Debye length. Using deionised (DI) water as pumping liquid, the EO pump generates 13.6 ml/min and 2 kPa at 150 V applied voltage. The power consumed by the pump is less than 0.4 W. The EO pump works without any bubbles in the hydraulic circuit. This design can be used to cool 47 W of power generated by the power components with a forced convection without evaporation and 270 W with evaporation
(Epi)transcriptomics in cardiovascular and neurological complications of COVID-19
Although systemic inflammation and pulmonary complications increase the mortality rate in COVID-19, a broad spectrum of cardiovascular and neurological complications can also contribute to significant morbidity and mortality. The molecular mechanisms underlying cardiovascular and neurological complications during and after SARS-CoV-2 infection are incompletely understood. Recently reported perturbations of the epitranscriptome of COVID-19 patients indicate that mechanisms including those derived from RNA modifications and non-coding RNAs may play a contributing role in the pathogenesis of COVID-19. In this review paper, we gathered recently published studies investigating (epi)transcriptomic fluctuations upon SARS-CoV-2 infection, focusing on the brain-heart axis since neurological and cardiovascular events and their sequelae are of utmost prevalence and importance in this disease
Reducing Instrumentation Overhead when Reverse-Engineering Object Interactions
Reverse-engineering object interactions from source
code can be done through static, dynamic, or hybrid (static plus
dynamic) analyses. In the latter two, monitoring a program and
collecting runtime information translates into some overhead
during program execution. Depending on the type of application,
the imposed overhead can reduce the precision and accuracy of
the reverse-engineered object interactions (the larger the overhead
the less precise or accurate the reverse-engineered interactions),
to such an extent that the reverse-engineered interactions
may not be correct, especially when reverse-engineering a multithreaded
software system. One is therefore seeking an instrumentation
strategy as less intrusive as possible. In our past work, we
showed that a hybrid approach is one step towards such a solution,
compared to a purely dynamic approach, and that there is
room for improvements. In this paper, we uncover, in a systematic
way, other aspects of the dynamic analysis that can be improved
to further reduce runtime overhead, and study alternative
solutions. Our experiments show effective overhead reduction
thanks to a modified procedure to collect runtime information
Geometric Exponents, SLE and Logarithmic Minimal Models
In statistical mechanics, observables are usually related to local degrees of
freedom such as the Q < 4 distinct states of the Q-state Potts models or the
heights of the restricted solid-on-solid models. In the continuum scaling
limit, these models are described by rational conformal field theories, namely
the minimal models M(p,p') for suitable p, p'. More generally, as in stochastic
Loewner evolution (SLE_kappa), one can consider observables related to nonlocal
degrees of freedom such as paths or boundaries of clusters. This leads to
fractal dimensions or geometric exponents related to values of conformal
dimensions not found among the finite sets of values allowed by the rational
minimal models. Working in the context of a loop gas with loop fugacity beta =
-2 cos(4 pi/kappa), we use Monte Carlo simulations to measure the fractal
dimensions of various geometric objects such as paths and the generalizations
of cluster mass, cluster hull, external perimeter and red bonds. Specializing
to the case where the SLE parameter kappa = 4p'/p is rational with p < p', we
argue that the geometric exponents are related to conformal dimensions found in
the infinitely extended Kac tables of the logarithmic minimal models LM(p,p').
These theories describe lattice systems with nonlocal degrees of freedom. We
present results for critical dense polymers LM(1,2), critical percolation
LM(2,3), the logarithmic Ising model LM(3,4), the logarithmic tricritical Ising
model LM(4,5) as well as LM(3,5). Our results are compared with rigourous
results from SLE_kappa, with predictions from theoretical physics and with
other numerical experiments. Throughout, we emphasize the relationships between
SLE_kappa, geometric exponents and the conformal dimensions of the underlying
CFTs.Comment: Added reference
A semi-classical field method for the equilibrium Bose gas and application to thermal vortices in two dimensions
We develop a semi-classical field method for the study of the weakly
interacting Bose gas at finite temperature, which, contrarily to the usual
classical field model, does not suffer from an ultraviolet cut-off dependence.
We apply the method to the study of thermal vortices in spatially homogeneous,
two-dimensional systems. We present numerical results for the vortex density
and the vortex pair distribution function. Insight in the physics of the system
is obtained by comparing the numerical results with the predictions of simple
analytical models. In particular, we calculate the activation energy required
to form a vortex pair at low temperature.Comment: 19 page
An exact reformulation of the Bose-Hubbard model in terms of a stochastic Gutzwiller ansatz
We extend our exact reformulation of the bosonic many-body problem in terms
of a stochastic Hartree ansatz to a stochastic Gutzwiller ansatz for the Bose
Hubbard model. This makes the corresponding Monte Carlo method more efficient
for strongly correlated bosonic phases like the Mott insulator phase or the
Tonks phase. We present a first numerical application of this stochastic method
to a system of impenetrable bosons on a 1D lattice showing the transition from
the discrete Tonks gas to the Mott phase as the chemical potential is
increased
A homomorphism between link and XXZ modules over the periodic Temperley-Lieb algebra
We study finite loop models on a lattice wrapped around a cylinder. A section
of the cylinder has N sites. We use a family of link modules over the periodic
Temperley-Lieb algebra EPTL_N(\beta, \alpha) introduced by Martin and Saleur,
and Graham and Lehrer. These are labeled by the numbers of sites N and of
defects d, and extend the standard modules of the original Temperley-Lieb
algebra. Beside the defining parameters \beta=u^2+u^{-2} with u=e^{i\lambda/2}
(weight of contractible loops) and \alpha (weight of non-contractible loops),
this family also depends on a twist parameter v that keeps track of how the
defects wind around the cylinder. The transfer matrix T_N(\lambda, \nu) depends
on the anisotropy \nu and the spectral parameter \lambda that fixes the model.
(The thermodynamic limit of T_N is believed to describe a conformal field
theory of central charge c=1-6\lambda^2/(\pi(\lambda-\pi)).)
The family of periodic XXZ Hamiltonians is extended to depend on this new
parameter v and the relationship between this family and the loop models is
established. The Gram determinant for the natural bilinear form on these link
modules is shown to factorize in terms of an intertwiner i_N^d between these
link representations and the eigenspaces of S^z of the XXZ models. This map is
shown to be an isomorphism for generic values of u and v and the critical
curves in the plane of these parameters for which i_N^d fails to be an
isomorphism are given.Comment: Replacement of "The Gram matrix as a connection between periodic loop
models and XXZ Hamiltonians", 31 page
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